Compass Detectors
Hi Snake
Compass had the B series 94B, 77B...high frequency 100 khz and did not discriminate beyond small iron.Wide scan loops 3,5,8 and 12 inches.
The 77B is still used because although it has little depth compared to modern machines you can detect where they won't go. Two or three or more nails will be ignored, if theres a coin under them it will pick up the coin.
The Judge Series, also 100khz, were TR discriminators and would reject or rather bypass much iron that would have to be positively discrimed out with other machines. Drawback heavy and only really suited to low/medium mineralisation areas.
The VLF Magnum Series. Coin Magnum Ground eliminating VLF discriminator. 5.73khz.Eliminated ground effects in discriminate mode when all other machines could only do it in all metal. Could detect nickels and rings whilst rejecting ring pulls. Drawback as always they were heavy. Discrimination system was odd. You could pick up a deep nickle in ring pull reject but shallow would be ignored.
Relic Magnum 7. 3.73khz (I think). Excellent for relics in the super deep all metal mode.
Magnum 420 10.5khz. Not the depth of the Magnum 7 but better discrimination. 8 and 12 inch widescan coils. There were cheaper less powerful versions of the 420, the 320 and 220. Weight 4lbs and used 6 AA batteries.
One drawback with most of the models was the Tri-Planner coils used. Most of the machines weighed 4 to 4.5lbs. The coil put a lot of the weight at end of the machine, the last place it was needed. Hip mounting or fitting an arm rest solved the problem.
There's also the motion range most of which have been re-introduced since they had the fire and restarted the business. Unfortunately the Challenger range...X70, 80,100 are no longer made though they were the flagship machines of the company so well worth looking for.